The invention relates to a method for controlling a hydropneumatic suspension of a mobile crane having at least four wheels which are each allocated a spring cylinder, having at least four spring circuits in which at least one spring cylinder is incorporated in each case, each spring circuit being allocated a pressure measurement sensor and a path measurement sensor, in which the signals of the pressure measurement sensor and of the path measurement sensor are processed by a control unit and the spring cylinders are actuated.
A hydropneumatic axle suspension for a mobile crane is already known from the German patent DE 35 46 704 C2. In order to achieve smooth travel operation during use of the mobile crane as a wrecker crane it is proposed, in the region of the rear vehicle axles, which are more heavily loaded by the towing operation, to separate the hydraulic cylinders thereof from their hydraulic accumulators by lockable valves and therefore to lock the suspension of the rear vehicle axles. In the region of the front vehicle axles the opposite hydraulic cylinders of at least one front axle are connected to one another via associated valves and are therefore switched to oscillation. The hydraulic cylinders of at least one of the front axles are also connected to a hydraulic accumulator with softer spring characteristics compared to those at the rear axles.
In the utility model DE 201 03 735 U1, a further hydropneumatic axle suspension for heavy goods vehicles, in particular mobile cranes with at least two axles, is described. Each wheel is allocated a hydraulic cylinder and, in the case of more than two axles, the hydraulic cylinders of the wheels, which are each allocated to one of the four corners of the vehicle, are respectively combined as a group to form an individually actuatable spring circuit. The hydraulic cylinders of a spring circuit are connected to a hydraulic accumulator via filling and discharge lines with filling and discharge valves. In addition, in each case a hydraulic cylinder of the at least three spring circuits is fitted with a path measurement sensor. In one exemplified embodiment, a mobile crane with four spring circuits is described. If the hydraulic cylinder has a path measurement sensor then it also has electronics which amplify the measurement signal of the path measurement sensor or convert it into a digital signal and transmit it to a central electronic control unit. The electronic control unit preferably has an electronic controller with preset level variations for the vehicle body so that automatic lifting and lowering of the at least three corners of the vehicle can be effected prior to the start of the lifting operation. The filling and discharge valves to the hydraulic accumulators are then closed for the lifting operation. A suspension—as absolutely necessary in road traffic—is then shut off.
Furthermore, in DE 10 2010 032 046 B4, a method is described for adjusting the level of a pneumatically suspended motor vehicle. In a conventional manner, the pneumatic-suspension comprises, for each wheel of the motor vehicle, a spring system consisting of at least one air spring, a pressure sensor and/or a position sensor. In pneumatic suspensions there is a direct relationship between the level—spring travel or stroke of the spring cylinder and pressure of the spring cylinder. Therefore, there is a proportionality factor with which a spring path deviation can be converted into a pressure deviation, and also a height-dependent set pressure component. Nevertheless, very different pressures may be present and twist the chassis of the motor vehicle.